Gonadotropin releasing hormone (GnRH) is the hypothalamic decapeptide which has a central role in the organization and timing of human sexual and reproductive function. Abnormal GnRH gene expression results in primary hypogonadism or precoccious puberty. GnRH and related peptides also occur in placenta and testes, where they may be important in maintaning placental function and fertility. It is therefore important to know the sites of GnRH synthesis, mechanisms available for control of synthesis, mode and control of release, and precursor structure. The studies in this proposal approach these goals directly by the isolation and characterization of GnRH hypothalamic messenger RNA, the cloning and nucleotide sequence analysis of the GnRH gene, and the design of cDNA probes for the quantification of GnRH-specific mRNA. Specifically, we wish to anwer the following questions: (1) Does a single gene encode GnRH and related peptides or are there multiple genes? (2) Is there a high molecular weight precursor for hypothalamic GnRH? Are additional peptides encoded by a common mRNA? (3) Are additional open reading frames encoded within the GnRH gene? (4) Is there a 5' gene sequence complementary to a signal peptide? (5) Are there 5' non-translated regions for transcriptional control, as initiation and steroid binding sites, within the GnRH gene? (6) Is the decapeptide pyroglu-his-trp-ser-tyr-gly-leu-arg-pro-glyNH2 the only form of GnRH in mammals or are there other partially homologous forms with overlapping functions? (7) Is expression of the GnRH gene(s) differentially regulated in hypothalamus, placenta and testes? Also the direct assessment of GnRH mRNA in complex physiological states will be made possible with the construction of highly specific exquisitely sensitive cDNA probes. Ultimately, this information will enable us to understand the physiology and pathology of GnRH gene expression in the hypothalamus, placenta and testes and to design biochemically specific therapy in related cases of abnormal puberty, placental pathology, and male infertility.